Entanglement, computation and quantum measurements
Vlatko Vedral · 2006
Abstract This chapter introduces a method that combines the concepts of quantum entanglement with those of quantum algorithms. In particular, some bounds are placed on the efficiency (speedup) of quantum computations by using the fact that there is a limit to how quickly entanglement can be generated with some operations. This method will truly exploit the “many-worlds” nature of quantum superpositions. By solving one problem using a superposition of qubits as well as solving a superposition of problems, the efficiency of some quantum tasks can be evaluated. This chapter demonstrates that a quantum search cannot be performed faster than the square root of the time of the corresponding classical search (winch is still very much faster). The use of entanglement to optimise quantum searches is discussed, along with a model for quantum measurement, similarity between quantum computation and a quantum measurement as described by von Neumann, correlations and quantum measurement, and the Bekenstein bound as an example of the ultimate limits of quantum computation.